The present invention relates to a device for removing bubbles entrained in a liquid such as industrial water (e.g. boiler water), fluids (including non-flammable fluids) used in hydraulic systems, slurries for ceramic materials, slurries used as coating solutions in paper-making machines for making coated paper, coating solutions for films and tapes, lubricants, cooling liquids for quenching, chemical solutions, liquid foodstuff, and so forth.
Bubbles entrained in a liquid of the kind described must be removed therefrom because they cause damage to equipment, increase compressivity, cause errosion due to cavitation, vibration and noise, result in poor product quality, and cause deterioration and change in quality of liquid.
There have been devices and demonstrated bubble removing methods in which the liquid is introduced into a cylinder or a coiled passage and bubbles entrained in the liquid are collected by means of the centrifugal force to the axis of the spiral flow and then are discharged.
In FIGS. 1 and 2 is shown an example of a device for practicing such method. A cylindrical body a, which is a vessel with an internal cylindrical space, is closed at its one or lower end by a lid b. An inlet port c, which is communicated with a liquid inflow pipe d, is disposed on the cylindrical body a close to the lid b such that a liquid flows into the cylindrical body a tangentially. The other end of the cylindrical body a is closed by a lid f to which is open an outlet port g which in turn is communicated with a liquid outlet pipe e. Reference letter h denotes a pump.
When a liquid with bubbles entrained therein is introduced through the inlet pipe d into the cylindrical body a, a gas column i indicated by two dot chain lines is formed depending upon the viscosity of the liquid and part of gases grow into large-sized bubbles which flow downstream. Therefore, when the outlet pipe e is connected to a tank, the large-sized bubbles float up by their own buoyancy and discharged.
This device in which large-sized bubbles are discharged downstream is advantageous in that there is no need of providing additional equipment such as an independent pipe for gas discharge or a gas suction pump.
However, it has the following problems:
(i) When bubbles flow through the outlet pipe e into the tank, they collide and are finely divided again.
(ii) On the way to the liquid surface in the tank, the bubbles are sucked by a liquid suction pump and therefore flow through a system line.
(iii) The diameter of the gas column i formed within the cylindrical body a is relatively large in comparison with the inner diameter of the cylindrical body a (sometimes it becomes almost two-thirds of the inner diameter of the cylindrical body a) and the liquid flows through the annular space defined between the gas column i and the inner wall surface of the cylindrical body a. As a result, the swirl radius of the liquid is increased so that the centrifugal force exerted to fine bubbles is decreased and consequently fine bubbles are not readily collected within the gas column i. In addition, the axial velocity of the liquid flowing through the annular space becomes high so that the axial component of the fluid force is increased and consequently bubbles flow downstream without being collected into large bubbles.
In order to solve these problems, it has been also proposed that a gas vent pipe j is incorporated at the inlet side of the device shown in FIGS. 1 and 2. That is, as shown in FIG. 3, the gas vent pipe j is connected centrally to the cylindrical body a through the lid b so that the gases may be discharged through the pipe j. However, even in such device, there are the following problems:
(i) Because of the single inlet port c, the swirl center k of the liquid does not coincide with the axis of the cylindrical body a under the influence of the fluid force as shown in FIG. 2; the swirl center k is variable depending upon variation of the liquid flow rate. Thus, the gas column i is not aligned with the gas vent pipe j so that usually the gases are not discharged through the pipe j; the gases are intermittently discharged only when the diameter of the gas column i is considerably increased. As a result, the bubble removal efficiency is low.
(ii) When the liquid flow rate is increased and the swirl velocity in the cylindrical body a is increased, the pressure in the cylindrical body at its inflow side is lowered into negative pressure, resulting in failure of discharging the gas.
The above-described devices are disclosed in the co-pending U.S. patent application No. 410,826.
The present invention was made to solve the above and other problems encountered in the prior art and has its object to provide a device for removing bubbles from a liquid in which the liquid is introduced through a plurality of equiangularly spaced inlet ports into a cylindrical body so that a stable spiral flow whose center coincides with the axis of the cylindrical body can be formed, thereby effectively collecting the bubbles and in which gases are discharged through a gas vent disposed, along the axis of the cylindrical body, in a portion for closing the cylindrical body at its inflow side so that the diameter of a gas column within the cylinder can be decreased, thereby further increasing the bubble collection efficiency and enhancing the bubble removal effect,
The present invention will become more apparent from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings.